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afoken
<p>In the old days of the WWW, AOL users were forced to use HTTP proxies provided by AOL. The setup had the annoying feature of using a different proxy for each request, so that the requests from a single user appeared to come from a large set of very different IP addresses, while each single IP address was used by a large set of users. Websites that assumed constant client IP addresses were unusable, websites that assumed one user per client IP address had huge security issues. I don't know if AOL still uses this setup, things have changed a lot since then. But as far as I know, this setup does not violate a single RFC, and websites that can't handle this setup are broken, period.</p>
<p>HTTP Proxies have become more and more popular, especially in corporate environments; mainly for security and for filtering / censoring unwanted content (mainly malware and porn sites). Many mobile internet providers offer a low cost connection that uses private IP addresses for the mobile device and a forced, transparent HTTP proxy to reduce the data volume in their mobile networks. But unlike AOL, they seem to use only a single proxy, or at least try not to change the proxy during a dialup session.</p>
<p>Big internet providers have several IPv4 address pools, simply because they had to request a new block from time to time. Those pools are not continuous, but fragmented. Dial-up (and DSL) clients get a random IP address from the pool, and with each new dial-up, the IP address may change wildly. Some providers use several small regional pools with perhaps two, three or four IP ranges, some have use a large common pool for the entire state with a large number of IP ranges.</p>
<p>At least in Germany, DSL connections are disconnected after 24 hours, and usually, the IP address changes after the reconnect. Fixed IPv4 addresses are available for extra money.</p>
<p>Alexander</p>
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Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
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